The present invention relates to methods of moving objects with a self-locking mechanical transmission, which can be used in linear and rotary drives.
Self-locking mechanical transmission, are well known, such as for example a screw-nut transmission, a worm--worm wheel transmission, etc. The movement with the screw-nut transmission is performed in the following manner; the rotation of the nut is prevented so that it can move only linearly, the screw is rotated and the rotation of the screw is transmitted to the nut to perform the linear movement. When the direction of rotation of the screw is changed, the direction of linear movement of the nut is reversed. It is also possible to allow only linear movement of the screw, and during rotation of the nut the screw will perform the linear movement.
The movement with the worm-worm wheel transmission is performed in the following manner; the worm is rotated and rotates the worm wheel. With a change of direction of rotation of the worm, the direction of rotation of the worm wheel is reversed.
A common feature of the above transmissions types are that they have a self-locking property, regardless of the nature of loading from an object to be moved. The loading of the object to be moved can be a resilient resistance or an external force such as a gravity force in the direction of movement. A self-locking transmission prevents undesired displacements in the transmissions. When a movement between a driving element and a driven element is performed frictional interaction substantially reduces the efficiency of such transmissions. Even with the use of lubricant the efficiency cannot be increased substantially.
A method of stepped movement of a self-locking transmission is known from my Soviet Inventor's Certificate number 1,401,209 (1986). This method includes causing oscillation of the driving element, a movement of the controlling element which is a screw in the screw-nut transmission in the phase of an idle running, and stopping of the controlling element in the phase of working running. Here a difference in the speeds of the driving and driven elements is determined. The direction of movement of the controlling element is changed during reversing of the movement of the driving element at the moment of negative difference of the speeds of the driving and driven elements. The controlling element is rolled or rotated over the driven element with the speed of movement of the controlling element equal or higher than the speed of movement of the driven element in the phase of an idle running. The controlling element is rolled over the driven element before stopping of the controlling element in phase of a working running. This known method is complicated since it requires additional change of the speed of the driving and driven elements. Moreover, the influence of a load, here a resilient force, prevents unloading of the controlling element. A negative difference in the speeds of the driving and driven elements is not provided.
A method of moving objects with a self-locking transmission is disclosed in my a Soviet Inventor's Certificate number 1,486,686 (1989). In accordance with this method, oscillations of a driving element in a self-locking transmission are generated. The element that is oscillated is a worm support in the worm--worm wheel transmission. A controlling element (a worm in a worm--worm wheel transmission) is displaced relative to the driven element in a phase of idle movement by low power motor. The lower power motor is braked and unbraked for the change of direction of oscillations of the controlling element. However, the use of the low power motor can only provide substantial power with a low movement speed. Thus, this motor does not provide efficient operation of a self-locking mechanical transmission. The presence of a torque on the motor during contacting of the driving and driven element does not lead to the braking of the driving element, and causes additional frictional interaction of the driving element with the driven element thereby reducing the efficiency of mechanical transmission. This also causes undesirable additional movements. Insufficiently fast interaction of the low power motor also does not provide a return of the driving element to an initial position. In addition to the change in the magnitude of movement the method leads to shocks and noise. Moreover, the influence of a load, for example resilient forces, causes constant braking by the driven element (screw in the screw-nut transmission or a worm wheel in the worm--worm wheel transmission) of the controlling element, whose unbraking becomes impossible for providing idle running.
In the above described methods, at the beginning of the working stroke there is always a gap between the driving element and the driven element, which leads to strikes, substantially reduces the reliability of operation of the transmission, and also causes noise. It is not always necessary to move the driving element back in the direction of a preceding position. However, when these known methods use oscillation one must return the driving element to the preceding position. Moving a driving element and a driven element only in the direction of travel of an object does not maintain a self-locking relationship between driving and driven elements. Also, it substantially reduces the reliability of operation of the transmission.